Antagonistic Potential Research Articles

In vitro inhibition mechanisms of Trichoderma yunnanense TM10 against Pyricularia oryzae and Rhizoctonia solani causing blast and sheath blight diseases in rice (Oryza sativa L.)

Blast and sheath blight diseases, caused by Pyricularia oryzae and Rhizoctonia solani, respectively, are major threats to rice production worldwide. Efforts should be made to limit the spread of these phytopathogens, preferably through sustainable methods. In this study, we investigated the antagonistic potential of the local isolate Trichoderma yunnanense TM10 against the pathogenic fungi P. oryzae and R. solani. The results demonstrated that T. yunnanense TM10 inhibited the growth of P. oryzae and R. solani through mechanisms such as competition, mycoparasitism, and antibiosis. Dual culture, filtrate culture, and double plate assays showed that T. yunnanense TM10 could inhibit the growth of both P. oryzae and R. solani. Slide culture and scanning electron microscope (SEM) tests confirmed that T. yunnanense TM10 exhibited mycoparasitic activity, including attachment, coiling, penetration, lysis, and destruction of pathogen hyphae. Additionally, T. yunnanense TM10 was capable of producing cell wall-degrading enzymes (CWDEs) such as chitinase and cellulase, as well as volatile organic compounds (VOCs) such as hydrogen cyanide (HCN). The multifaceted abilities of T. yunnanense TM10 for limiting the growth of P. oryzae and R. solani underscore its potential as an effective biocontrol agent for enhancing productivity and sustainability in rice cultivation.

Biocontrol Potential of a Native Trichoderma Collection Against Fusarium oxysporum f. sp. cubense Subtropical Race 4

The Canary Islands lead banana (Musa acuminata) production in the EU. Different fungal pathogens affect this crop in subtropical areas, with Fusarium oxysporum f. sp. cubense subtropical race 4 (Foc-STR4) being the most important in the Canary Islands. With the aim of developing environmentally sustainable techniques for disease control, this study presents the results of the evaluation of the antifungal capacity of a native Trichoderma collection (12 species, 109 isolates) obtained from banana soils. The results demonstrate the diversity of biocontrol genes and the in vitro antagonistic potential of different native Trichoderma species/isolates against two Foc-STR4 strains obtained from plants with Panama disease symptoms. Trichoderma virens (TF18), a dominant species in banana soils in the Canary Islands, showed a high capacity to inhibit the growth of Foc-STR4 in different in vitro assays. Trichoderma atrobrunneum (TF01) showed mycoparasitism capacity through the spiral coil around the hyphae of the pathogen. In addition, the genome analysis of T. atrobrunneum (TF03) showed 69 putative biosynthetic gene clusters, with the notable presence of the trichothecene tri5 gene. Finally, our work demonstrates that the soils of the Canary Islands banana crops are a potential source of environmentally adapted biological control agents to control or reduce the incidence of Foc-STR4.

Integrated large-scale metagenome assembly and multi-kingdom network analyses identify sex differences in the human nasal microbiome.

Respiratory diseases impose an immense health burden worldwide. Epidemiological studies have revealed extensive disparities in the incidence and severity of respiratory tract infections between men and women. It has been hypothesized that there might also be a nasal microbiome axis contributing to the observed sex disparities. Here, we study the nasal microbiome of healthy young adults in the largest cohort to date with 1593 individuals, using shotgun metagenomic sequencing. We compile the most comprehensive reference catalog for the nasal bacterial community containing 4197 metagenome-assembled genomes and integrate the mycobiome, to provide a valuable resource and a more holistic perspective for the understudied human nasal microbiome. We systematically evaluate sex differences and reveal extensive sex-specific features in both taxonomic and functional levels in the nasal microbiome. Through network analyses, we capture markedly higher ecological stability and antagonistic potentials in the female nasal microbiome compared to the male's. The analysis of the keystone bacteria reveals that the sex-dependent evolutionary characteristics might have contributed to these differences. In summary, we construct the most comprehensive catalog of metagenome-assembled-genomes for the nasal bacterial community to provide a valuable resource for the understudied human nasal microbiome. On top of that, comparative analysis in relative abundance and microbial co-occurrence networks identify extensive sex differences in the respiratory tract community, which may help to further our understanding of the observed sex disparities in the respiratory diseases.

Biological Suppression of Sclerotium rolfsii in Groundnut Cultivation: A Path Towards Sustainable Disease Management

Stem rot of groundnut caused by Sclerotium rolfsii Sacc, is a major soil borne disease which impact on groundnut cultivation both in India and globally. The primary objective of this study was to assess the antagonistic potential of biocontrol agents against the pathogen, both individually and in combination, under In vitro and glasshouse conditions. The results of the present investigation indicated that the application of microbial consortia was more effective against Sclerotium rolfsii than individual bioagents. Specifically, seed treatment with microbial consortia MC1, MC2, MC3, and MC4 resulted in lower disease incidence with 13.80%, 16.01%, 20.0%, and 22.60% respectively, compared to the pathogen check, which had a 74.12% PDI. Additionally, these treatments also enhanced plant growth through improved plant growth-promoting traits under glasshouse conditions.

The microbiome of continuous wheat rotations: minor shifts in bacterial and archaeal communities but a source for functionally active plant-beneficial bacteria

Continuous wheat cropping often leads to yield decline, with suspected causes including increased pathogen susceptibility, decreased root growth, or low nutrient use efficiency, though the exact causes remain unknown. Here, we investigated soil and root-associated bacterial and archaeal communities in wheat under rotation versus continuous cultivation, monitored fungal pathogen presence, and used beneficial bacteria to mitigate Gaeumannomyces tritici (Ggt) symptoms in greenhouse experiments. Sampling was conducted at two field sites with different soil textures over two years and at two plant developmental stages, capturing site-specific and seasonal fluctuations. By cultivation, 767 bacterial isolates were screened for plant-beneficial traits. Amplicon sequencing revealed minor effects on community structure due to wheat rotational position but pronounced effects related to site, year, and microhabitat. Rhizoplane isolates with plant-beneficial traits were mainly Flavobacterium, Microbacterium, Pedobacter, Pseudomonas, Stenotrophomonas, and Variovorax. Continuous wheat rotations showed the highest proportion of bacteria with fungal antagonistic potential, indicating plant roots’ recruitment of beneficial bacteria. Introducing Ggt in the greenhouse experiment altered the bacterial and archaeal community, confirming field study results and demonstrating that applying beneficial bacteria early in the season at the seedling stage can control Ggt and improve plant growth. This study highlights the dynamic nature of wheat's below-ground bacterial and archaeal community, influenced by soil type, season, and microhabitat, with wheat rotation playing a minor role. In addition, it confirms the potential of selected Bacillus and Pseudomonas isolates, whether used individually or in consortia, for microbe-assisted mitigation of yield decline in intensive wheat production.

Identification and Antagonistic Potential of Bacillus atrophaeus against Wheat Crown Rot Caused by Fusarium pseudograminearum

Fusarium pseudograminearum (Fpg) is a significant pathogen responsible for fusarium crown rot (FCR) in wheat (Triticum aestivum L.), a disease with devastating impacts on crop yield. The utilization of biocontrol bacteria to combat fungal diseases in plants is a cost-effective, eco-friendly, and sustainable strategy. In this trial, an endophytic bacterial species, designated as SW, was isolated from the roots of wheat. The strain exhibited potent antagonistic effects against Fpg and reduced the FCR disease severity index by 76.07 ± 0.33% in a greenhouse pot trial. Here, 106 colony-forming units (CFUs)/mL of the SW strain was determined to be the minimum dose required to exhibit the antagonism against Fpg. The strain was identified as Bacillus atrophaeus using genome sequencing and comparison with type strains in the NCBI database. Whole-genome sequencing analysis revealed that SW harbors genes for siderophores, antifungal metabolites, and antibiotics, which are key contributors to its antagonistic activity. Additionally, the strain’s ability to utilize various carbon and nitrogen sources, successfully colonize wheat root tissues as an endophyte, and form biofilms are critical attributes for promoting plant growth. In summary, these findings demonstrate the ability of Bacillus atrophaeus to control FCR disease in wheat in a sustainable agricultural setting.

Co-existence of two antibiotic-producing marine bacteria: Pseudoalteromonas piscicida reduce gene expression and production of the antibacterial compound, tropodithietic acid, in Phaeobacter sp.

Many bacteria co-exist and produce antibiotics, yet we know little about how they cope and occupy the same niche. The purpose of the present study was to determine if and how two potent antibiotic-producing marine bacteria influence the secondary metabolome of each other. We established an agar- and broth-based system allowing co-existence of a Phaeobacter species and Pseudoalteromonas piscicida that, respectively, produce tropodithietic acid (TDA) and bromoalterochromides (BACs). Co-culturing of Phaeobacter sp. strain A36a-5a on Marine Agar with P. piscicida strain B39bio caused a reduction of TDA production in the Phaeobacter colony. We constructed a transcriptional gene reporter fusion in the tdaC gene in the TDA biosynthetic pathway in Phaeobacter and demonstrated that the reduction of TDA by P. piscicida was due to the suppression of the TDA biosynthesis. A stable liquid co-cultivation system was developed, and the expression of tdaC in Phaeobacter was reduced eightfold lower (per cell) in the co-culture compared to the monoculture. Mass spectrometry imaging of co-cultured colonies revealed a reduction of TDA and indicated that BACs diffused into the Phaeobacter colony. BACs were purified from Pseudoalteromonas; however, when added as pure compounds or a mixture they did not influence TDA production. In co-culture, the metabolome was dominated by Pseudoalteromonas features indicating that production of other Phaeobacter compounds besides TDA was reduced. In conclusion, co-existence of two antibiotic-producing bacteria may be allowed by one causing reduction in the antagonistic potential of the other. The reduction (here of TDA) was not caused by degradation but by a yet uncharacterized mechanism allowing Pseudoalteromonas to reduce expression of the TDA biosynthetic pathway.IMPORTANCEThe drug potential of antimicrobial secondary metabolites has been the main driver of research into these compounds. However, in recent years, their natural role in microbial systems and microbiomes has become important to determine the assembly and development of microbiomes. Herein, we demonstrate that two potent antibiotic-producing bacteria can co-exist, and one mechanism allowing the co-existence is the specific reduction of antibiotic production in one bacterium by the other. Understanding the molecular mechanisms in complex interactions provides insights for applied uses, such as when developing TDA-producing bacteria for use as biocontrol in aquaculture.

Harnessing the antagonistic potential and unraveling the bioactive compounds of Streptomyces sp. isolate WAB2 to protect watermelon crop from Colletotrichum orbiculare

ABSTRACT Watermelon (Citrullus lanatus Thumb) is a significant vegetable crop globally and is prone to anthracnose disease caused by Colletotrichum spp. The use of chemical fungicides for managing crop diseases has adverse impacts on the environment and human health. Therefore, it is important to use biocontrol agents for disease management. In this study, streptomycetes were assessed as a potential biocontrol agent against anthracnose pathogen, Colletotrichum orbiculare WEC2. The potent Streptomyces sp. isolate WAB2 was isolated from healthy watermelon plants and showed remarkable antifungal efficacy against C. orbiculare WEC2. Rigorous assays confirmed its performance against C. orbiculare WEC2. Bioactive compounds produced by Streptomyces sp. isolate WAB2 were identified using Gas Chromatography–Mass Spectrometry (GC–MS). An SEM study indicated the parasitic action of Streptomyces sp. isolate WAB2 against the pathogen. The formulated talc-based product of Streptomyces sp. isolate WAB2 was effective when applied as a seed treatment + foliar spray against C. orbiculare WEC2 under pot culture conditions. These treatments reduced the disease incidence (31.81%) and exhibited a higher disease reduction (52.56%), compared to the untreated control. Therefore, treatment with talc-based Streptomyces sp. isolate WAB2 is a sustainable solution for anthracnose disease management, and it facilitates eco-friendly crop protection practices against the disease in watermelon. RESEARCH HIGHLIGHTS Isolated streptomycete strains from healthy watermelon plants and screened for its efficacy against the pathogen, Colletotrichum orbiculare WEC2. Streptomyces sp. isolate WAB2 showed significant antifungal activity against the pathogen. Bio-active compounds produced by Streptomyces sp. isolate WAB2 was identified by Gas Chromatography–Mass Spectrometry (GC–MS). Using scanning electron microscopy (SEM), the parasitic activity of Streptomyces sp. isolate WAB2 against the pathogen was detected. Developed a talc-based formulation of Streptomyces sp. isolate WAB2 and tested it as a seed treatment plus foliar spray, effectively reducing the disease incidence.

The Public Health Risks of β-Hemolytic Bacillus pumilus Bacteria Resistant to Gastrointestinal Conditions from Medicinal Plant.

In numerous countries, the utilization of plants for both nutritional and therapeutic purposes is a common practice. However, the inadvertent use of these plants can pose risks due to their active molecules or microbiota. The traditional use of Herniaria glabra L. (H. glabra) plant in treating various diseases is well-known; however, its application in yogurt production raises concerns. In this study, Bacillus pumilus isolated from H. glabra was identified through 16s rRNA sequencing and MALDI-TOF MS (Matriks Assisted Lazer Desorption Ionization Time of Flight Massspectrometry). The bacterium's resistance under simulated gastrointestinal tract (GIT) conditions was assessed, followed by investigations into its aggregation ability, antibiotic resistance, hemolytic activity, and antagonistic potential through in vitro tests. The study revealed that B. pumilus exhibited 100% resistance to GIT conditions. Notably, the bacterium demonstrated strong autoaggregation (34.48%) and coaggregation abilities (49.82% for Escherichia coli, 49.13% for Listeria monocytogenes), signifying a potent aggregative potential. Sensitivity to most tested antibiotics was observed, while no antagonistic activity against tested bacteria was evident. Furthermore, the bacterium exhibited β-hemolytic activity, indicative of potential virulence. The findings suggest that this resistant yet virulent bacterium, with its hemolytic activity, could disrupt the GIT balance, posing serious health risks. The study underscores the need for caution and awareness regarding the potential dangers posed by bacteria in plant microbiota in herbal therapies.

Loop-mediated isothermal amplification (LAMP) assay proved the mechanism of biological control against root rot pathogens

BackgroundThe soil-borne fungi, Rhizoctonia solani and Sclerotium rolfsii, are major pathogens of Brassicae crops. This study was performed to clarify the relationship between the accumulation pattern of the genus Trichoderma and disease suppression in frequently inoculated soils with binucleate Rhizoctonia (BNR), Rhizoctonia solani and Sclerotium rolfsii.ResultsAs compared to the control group, five Trichoderma virens strains isolated from soil inoculated with R. solani or BNR significantly reduced the severity of S. rolfsii (85.6–100% covering percentage) and R. solani (95.7–100% covering percentage). Similarly, five T. hamatum strains obtained from soil inoculated with R. solani were shown to be highly suppressive against S. rolfsii (83.9–97.1% covering percentages) and R. solani (60.2–96.2% covering percentages). Four out of five T. hamatum strains obtained from soil infected with S. rolfsii exhibited considerable suppression against S. rolfsii (63.7–91.2% covering percentages), while the SM5 strain did not. The phylogenetic analysis of the TEF and ITS regions of Trichoderma hamatum revealed that most isolates were classified into the same cluster with homology of 99–100%. Five strains of each T. virens and T. hamatum were isolated from the suppressive soil with high antagonistic potentials against R. solani and S. rolfsii. Suppression and antagonistic activity of T. hamatum isolated from soil frequently inoculated with sterile barley grains were negligible, whereas T. hamatum isolated from frequently inoculated soil with BNR and R. solani demonstrated considerable suppression of the pathogens and antagonistic activity. Accumulation and quantification of T. virens and T. hamatum were confirmed using loop-mediated isothermal amplification (LAMP).ConclusionIn conclusion, disease suppression in frequently inoculated soil with BNR, R. solani and S. rolfsii was due to Trichoderma spp. accumulated selectively in each replicate of soil inoculation.

Differential Interactions of Flavonoids with the Aryl Hydrocarbon Receptor In Silico and Their Impact on Receptor Activity In Vitro.

The molecular mechanisms underlying the observed anticancer effects of flavonoids remain unclear. Increasing evidence shows that the aryl hydrocarbon receptor (AHR) plays a crucial role in neoplastic disease progression, establishing it as a potential drug target. This study evaluated the potential of hydroxy flavonoids, known for their anticancer properties, to interact with AHR, both in silico and in vitro, aiming to understand the mechanisms of action and identify selective AHR modulators. A PAS-B domain homology model was constructed to evaluate in silico interactions of chrysin, naringenin, quercetin apigenin and agathisflavone. The EROD activity assay measured the effects of flavonoids on AHR's activity in human breast cancer cells (MCF7). Simulations showed that chrysin, apigenin, naringenin, and quercetin have the highest AHR binding affinity scores (-13.14 to -15.31), while agathisflavone showed low scores (-0.57 and -5.14). All tested flavonoids had the potential to inhibit AHR activity in a dose-dependent manner in the presence of an agonist (TCDD) in vitro. This study elucidates the distinct modulatory effects of flavonoids on AHR, emphasizing naringenin's newly described antagonistic potential. It underscores the importance of understanding flavonoid's molecular mechanisms, which is crucial for developing novel cancer therapies based on these molecules.

Root Rot Management in Common Bean (Phaseolus vulgaris L.) Through Integrated Biocontrol Strategies using Metabolites from Trichoderma harzianum, Serratia marcescens, and Vermicompost Tea

Common bean (Phaseolus vulgaris L.) is an essential food staple and source of income for small-holder farmers across Africa. However, yields are greatly threatened by fungal diseases like root rot induced by Rhizoctonia solani. This study aimed to evaluate an integrated approach utilizing vermicompost tea (VCT) and antagonistic microbes for effective and sustainable management of R. solani root rot in common beans. Fourteen fungal strains were first isolated from infected common bean plants collected across three Egyptian governorates, with R. solani being the most virulent isolate with 50% dominance. Subsequently, the antagonistic potential of vermicompost tea (VCT), Serratia sp., and Trichoderma sp. was assessed against this destructive pathogen. Combinations of 10% VCT and the biocontrol agent isolates displayed potent inhibition of R. solani growth in vitro, prompting in planta testing. Under greenhouse conditions, integrated applications of 5 or 10% VCT with Serratia marcescens, Trichoderma harzianum, or effective microorganisms (EM1) afforded up to 95% protection against pre- and post-emergence damping-off induced by R. solani in common bean cv. Giza 6. Similarly, under field conditions, combining VCT with EM1 (VCT + EM1) or Trichoderma harzianum (VCT + Trichoderma harzianum) substantially suppressed disease severity by 65.6% and 64.34%, respectively, relative to untreated plants. These treatments also elicited defense enzyme activity and distinctly improved growth parameters including 136.68% and 132.49% increases in pod weight per plant over control plants. GC–MS profiling of Trichoderma harzianum, Serratia marcescens, and vermicompost tea (VCT) extracts revealed unique compounds dominated by cyclic pregnane, fatty acid methyl esters, linoleic acid derivatives, and free fatty acids like oleic, palmitic, and stearic acids with confirmed biocontrol and plant growth-promoting activities. The results verify VCT-mediated delivery of synergistic microbial consortia as a sustainable platform for integrated management of debilitating soil-borne diseases, enhancing productivity and incomes for smallholder bean farmers through regeneration of soil health. Further large-scale validation can pave the adoption of this climate-resilient approach for securing food and nutrition security.

Salinity-induced variations in wheat biomass are regulated by the Na+:K+ ratio, root exudates, and keystone species

Salt stress can limit crop productivity, and there are differences in salt tolerance among plant varieties; however, we lack a comprehensive understanding of how keystone species obtained from different plant varieties under salt stress change plant biomass by driving root exudate secretion and regulating the Na+:K+ ratio. We conducted a pot experiment for three wheat varieties (JiMai32 (JM32), XiaoYan60 (XY60), and ShanRong3 (SR3)) under saline/nonsaline soil conditions. Salt stress tended to significantly reduce wheat biomass, and the biomass reduction rates of the different varieties decreased in the order JM32 < XY60 < SR3. The compositions of the bacterial and fungal communities in the root endosphere, rhizosphere and bulk soil were measured, and salt-induced microbial taxa were isolated to identify keystone species from the co-occurrence networks and to study their effects on physiological responses to salinity in wheat varieties. We observed that root exudates participated in the regulation of the Na+:K+ ratio, thereby affecting wheat biomass, and this process was regulated by keystone species. JM32 was enriched in microorganisms that promote plant growth and resistance to salt stress, such as Burkholderiales, Sordariomycetes, Alteromonadaceae, Acremonium, and Dokdonella, and inhibited microorganisms that are sensitive to the environment (salt, nutrients) and plant pathogens, such as Nocardioidaceae, Nitrospira, Cytophagaceae, Syntrophobacteriaceae, and Striaticonidium. XY60 inhibited microorganisms with biological control and disease inhibition potential, such as Agromyces and Kaistobacter. SR3-enriched pathogens, such as Aurantimonadaceae and Pseudogymnoascus, as well as microorganisms with antagonistic pathogen potential and the ability to treat bacterial infections, such as RB41 and Saccharothrix, were inhibited. Our results confirmed the crucial function of salt-induced keystone species in enhancing plant adaptation to salt stress by driving root exudate secretion and regulating the Na+:K+ ratio, with implications for exploring reasonable measures to improve plant salt tolerance.

Screening (ant)agonistic activities of xenobiotics on the retinoic acid receptor alpha (RARα) using in vitro and in silico analysis

Retinoic acid receptors (RARs) are known as crucial endocrine receptors that could mediate a broad diversity of biological processes. However, the data on endocrine disrupting effects of emerging chemicals by targeting RAR (ant)agonism are far from sufficient. Herein, we investigated the RARα agonistic or antagonistic activities for 75 emerging chemicals of concern, and explored their interactions with this receptor. A recombinant two-hybrid yeast assay was used to examine the RARα activities of the test chemicals, wherein 7 showed effects of RARα agonism and 54 exerted potentials of RARα antagonism. The representative chemicals with RARα agonistic activities, i.e. 4-hydroxylphenol (4-HP) and bisphenol AF (BPAF), significantly increased the mRNA levels of CRABP2 and CYP26A1, while 4 select chemicals with RARα antagonistic potentials, including bisphenol A (BPA), tetrabromobisphenol A (TBBPA), 4-tert-octylphenol (4-t-OP), and 4-n-nonylphenol (4-n-NP), conversely decreased the transcriptional levels of the test genes. The in silico molecular docking analysis using 3 different approaches further confirmed the substantial binding between the chemicals with RARα activities and this nuclear receptor protein. This work highlights the promising strategy for screening endocrine-disrupting effects of emerging chemicals of concern by targeting RARα (ant)agonism.

Biostimulant and antagonistic potential of endophytic fungi against fusarium wilt pathogen of tomato Fusarium oxysporum f. sp. lycopersici

Endophytic fungal-based biopesticides are sustainable and ecologically-friendly biocontrol agents of several pests and diseases. However, their potential in managing tomato fusarium wilt disease (FWD) remains unexploited. This study therefore evaluated effectiveness of nine fungal isolates against tomato fusarium wilt pathogen, Fusarium oxysporum f. sp. lycopersici (FOL) in vitro using dual culture and co-culture assays. The efficacy of three potent endophytes that inhibited the pathogen in vitro was assessed against FWD incidence, severity, and ability to enhance growth and yield of tomatoes in planta. The ability of endophytically-colonized tomato (Solanum lycopersicum L.) plants to systemically defend themselves upon exposure to FOL were also assessed through defence genes expression using qPCR. In vitro assays showed that endophytes inhibited and suppressed FOL mycelial growth better than entomopathogenic fungi (EPF). Endophytes Trichoderma asperellum M2RT4, Hypocrea lixii F3ST1, Trichoderma harzianum KF2R41, and Trichoderma atroviride ICIPE 710 had the highest (68.84–99.61%) suppression and FOL radial growth inhibition rates compared to EPF which exhibited lowest (27.05–40.63%) inhibition rates. Endophytes T. asperellum M2RT4, H. lixii F3ST1 and T. harzianum KF2R41 colonized all tomato plant parts. During the in planta experiment, endophytically-colonized and FOL-infected tomato plants showed significant reduction of FWD incidence and severity compared to non-inoculated plants. In addition, these endophytes contributed to improved growth promotion parameters and yield. Moreover, there was significantly higher expression of tomato defence genes in T. asperellum M2RT4 colonized than in un-inoculated tomato plants. These findings demonstrated that H. lixii F3ST1 and T. asperellum M2RT4 are effective biocontrol agents against FWD and could sustainably mitigate tomato yield losses associated with fusarium wilt.

PLANT-GROWTH-PROMOTING AND ANTIFUNGAL ASSET OF INDIGENOUS DROUGHT-TOLERANT RHIZOBACTERIA ISOLATED FROM OLIVE (Olea europaea L.) RHIZOSPHERE

Faced with global environmental challenges, the quest for sustainable food production has gathered momentum. While abiotic stresses adversely affect plant health and productivity, Verticillium wilt causes considerable yield losses worldwide, particularly in crops such as olive. Recently, drought-tolerant bacteria have been used to alleviate both abiotic stress and pathogen pressure in crops. In this context, our work focuses on the isolation of tolerant indigenous rhizobacteria to mitigate these challenges by investigating their role in biocontrol and abiotic stress tolerance. Thus, a total of 94 rhizobacterial strains were isolated from the rhizospheres of olive trees in southeastern Morocco and characterized to identify tolerant plant growth-promoting rhizobacteria that inhibit Verticillium dahliae. 24 strains demonstrated in vitro suppression of Verticillium dahliae Klebahn, and exhibited tolerance to different abiotic stresses (drought, salinity, and high temperature). In addition, they proved xerotolerant (Aw ≤ 0.91), halotolerant (≥10% NaCl), and thermotolerant (≥ 55°C) capabilities. Beyond, these isolates showcased multifaceted plant growth-promoting traits, such as phosphate solubilization and significant synthesis of essential bioactive compounds like siderophores, indole-3-acetic acid and hydrolytic enzymes. Evaluating outcomes, three standout rhizobacterial isolates emerged due to their exceptional stress tolerance, unique plant growth-promoting qualities, and potent antagonistic potential. Molecular analysis identified them as Bacillus paranthracis (OZ-60) and Bacillus licheniformis (OZ-48 and OZ-77) through 16S rRNA sequencing. Besides enhancing plant abiotic stress resistance, these isolates hold promise in bolstering the sustainability of olive cultivation and fortifying plant defenses against pathogens.

Identification and Evaluation of Antagonistic Potential of Different fluorescent pseudomonads in Northern Plains of West Bengal

To achieve future food security, reliable crop protection will be critically important. Development of biological control for soil borne disease is accepted as a safe, durable and ecofriendly alternative for chemical management strategy. Pseudomonads possess many traits like production antibiotics, lytic enzymes, siderophores, hydrogen cyanide (HCN) that make them well suited as biocontrol and growth-promoting agents. An attempt was taken to isolate and identify different fluorescent Pseudomonads and to evaluate their antagonistic ability. Twelve fluorescent Pseudomonads isolates were collected from different crop rhizosphere from different locations of northern parts of West Bengal. Isolates characterized morphologically and biochemically. All the isolates were gram negative rods with smooth and glossy colony on kings B and nutrient agar medium with convex elevation but variation was found in respect to pigment production. A huge variation was found in respect to biochemical characterization. From the result of biochemical analysis, the isolated sp. can be identified as Pseudomonas fluorescens or Pseudomonas putida or Pseudomonas aeruginosa. Some of the isolate produce green, some isolates produce yellowish green and rest of them produce red/pink pigments. Isolates showed a huge variation in respect to pathogenicity against soil borne pathogen Slerotium rolfsii. Percent inhibition varied from 31 to 74 %. Isolate 3 and 8 can be efficient biocontrol agent as highest growth inhibition of the pathogen Sclerotium rolfsii was obtained by the isolate 8 (74.37%) followed by isolate 3 (63.15%). In respect to growth parameter isolate 8, 9 and 10 were found better among the isolates where as in respect to disease reduction isolate 3, 8, 9 and 11 were promising under in vivo study.

Antagonistic Potential of Ascorbic Acid and SiO2 Against Fusarium oxysporium, the Causative of Damping–off Disease in Melon Seedlings

Antagonistic Potential of Ascorbic Acid and SiO2 Against Fusarium oxysporium, the Causative of Damping–off Disease in Melon Seedlings

Multiple Chitin- or Avirulent Strain-Triggered Immunity Induces Microbiome Reassembly in Rice.

Magnaporthe oryzae is one of the most important fungal pathogens of rice. Chitin and avirulent strains can induce two layers of immunity response, pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and effector-triggered immunity (ETI), in rice with cognate R genes. However, little is known about the assembly of the rice microbiome induced by PTI and ETI in rice. In this study, we investigate the impact of continuous treatment of the avirulent M. oryzae strain with AvrPi9 and chitin on the bacterial endophytic community of rice varieties harboring resistant gene Pi9 and their antagonistic activity against rice blast fungus. Analysis of the 16S rRNA showed a significant increase in the diversity and microbial co-occurrence network complexity and the number of beneficial taxa-Bacillus, Pseudomonas, Microbacterium, and Stenotrophomonas spp.-following the chitin and avirulent strain treatments. The antifungal assay with bacterial endophytes recovered from the leaves showed few bacteria with antagonistic potential in rice treated with avirulent strains, suggesting that the sequential treatment of the avirulent strain decreased the antagonistic bacteria against M. oryzae. Moreover, we identified Bacillus safensis Ch_66 and Bacillus altitudinis Nc_68 with overall antagonistic activities in vivo and in vitro. Our findings provide a novel insight into rice microbiome assembly in response to different innate immunity reactions.

Improved physiological responses and stress tolerance in cotton against Fusarium wilt with Trichoderma harzianum treatment

Cotton is a vital cash crop in the agricultural economy. Many abiotic stresses and pathogenic diseases reduce cotton yield, with cotton wilt being a major threat caused by Fusarium oxysporum f.sp. vasinfectum (FOV). In the present study, the antagonistic potential of Trichoderma harzianum, along with its extracted volatile and non-volatile compounds, was evaluated against FOV. In a dual culture assay, T. harzianum showed 71.4% inhibition of FOV. The volatile compounds extracted from T. harzianum showed 54.9% inhibition of FOV, while the non-volatile compounds reduced the growth of F. oxysporum f.sp. vasinfectum by 64.21%. The evaluation of vegetative traits of cotton plants indicated increased biomass when treated with T. harzianum. The activity of antioxidant defense enzymes Catalase activity (CAT), Superoxide dismutase activity (SOD), and Peroxidase activity (POX) was highest in cotton plants treated with both T. harzianum and F. oxysporum f.sp. vasinfectum, indicating an activation of the plant defense mechanisms in response to these treatments. Protein content, Malondialdehyde Content (MDA), proline content, electrolyte leakage, and H2O2 content, which are stress markers, were at their maximum under F. oxysporum f.sp. vasinfectum stress. Physiological features, including stomatal conductance, photosynthesis rate, Soil Plant Analysis Development (SPAD) chlorophyll value, and relative water content, were highest in plants treated with T. harzianum, as T. harzianum improves and boosts plant growth. Hence, T. harzianum is an effective biological control agent against FOV.